Sensing device and driving method of sensing device

ABSTRACT

A sensing device includes a plurality of sensing electrodes arranged in a row direction and a column direction, a sensing circuit including a plurality of read-out circuits respectively connected to the plurality of sensing electrodes and a control circuit for controlling the plurality of read-out circuits, and an arithmetic circuit that arithmetically is configured to process a sensing signal output from the sensing circuit. The plurality of sensing circuits and the plurality of read-out circuits are connected one-to-one via wiring. The sensing circuit is configured to store a driving table storing multiple sampling frequencies different from each other. The control circuit is configured to read out the multiple sampling frequencies, drives simultaneously the plurality of read-out circuits at the multiple sampling frequencies, and output a plurality of output signals to the arithmetic circuit. The arithmetic circuit is configured to calculate the amount of noise using the multiple sampling frequencies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from the prior JapanesePatent Application No. 2022-019511 filed on Feb. 10, 2022, the entirecontents of which are incorporated herein by reference.

FIELD

An embodiment of the present invention relates to a sensing device and adriving method of the sensing device.

BACKGROUND

A touch panel is known as an interface for a user to input information.For example, the touch panel detects coordinates of a sensing object(for example, user's finger or a touch pen) in contact with the touchpanel by using a signal input to a sensor provided on the touch panel.

For example, when noise is superimposed on a signal input to the sensor,there is a possibility that an error occurs between the coordinates ofthe sensing object sensed by the touch panel and the coordinates of theactual sensing object. On the other hand, in recent years, a touch paneldevice that can easily determine the presence or absence of noisewithout using a complicated filter technique has been developed.

SUMMARY

A sensing device in an embodiment according to the present inventionincludes a plurality of sensing electrodes arranged in a row directionand a column direction, a sensing circuit including a plurality ofread-out circuits respectively connected to the plurality of sensingelectrodes and a control circuit for controlling the plurality ofread-out circuits, and an arithmetic circuit that processes a sensingsignal output from the sensing circuit, wherein the plurality of sensingelectrodes and the plurality of read-out circuits are connectedone-to-one via wiring, the sensing circuit is configured to store adriving table that stores multiple sampling frequencies different fromeach other, the control circuit is configured to read out the multiplesampling frequencies from the driving table, drive simultaneously theplurality of read-out circuits by using the multiple samplingfrequencies, and output a plurality of output signals obtained by thedriving to the arithmetic circuit, and the arithmetic circuit isconfigured to process the plurality of output signals from the controlcircuit, and to calculate the amount of noise.

A driving method of a sensing device in an embodiment according to thepresent invention includes the sensing device including a plurality ofsensing electrodes arranged in a row direction and a column direction, asensing circuit including a plurality of read-out circuits respectivelyconnected to the plurality of sensing electrodes and a control circuitfor controlling the plurality of read-out circuits, and an arithmeticcircuit that arithmetically processes a sensing signal output from thesensing circuit, the plurality of sensing circuits and the plurality ofread-out circuits are connected one-to-one via wiring, the sensingcircuit stores a driving table that stores multiple sampling frequenciesdifferent from each other, reading out the multiple sampling frequenciesdifferent from each other, driving simultaneously the plurality ofread-out circuits at the multiple sampling frequencies different fromeach other, generating a plurality of output signals obtained by thedriving, performing arithmetic processing on the plurality of outputsignals read-out using the multiple sampling frequencies different fromeach other, and calculating the amount of noise.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic plan view showing a configuration of a sensingdevice according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an example of the detection of avoltage change in the self-capacitance method.

FIG. 3 is a schematic cross-sectional view of a sensing panel accordingto an embodiment of the present invention.

FIG. 4 is a block diagram showing a functional configuration of asensing device according to an embodiment of the present invention.

FIG. 5 is a timing chart for explaining a driving method of a sensingdevice according to an embodiment of the present invention.

FIG. 6 is a diagram for explaining a driving method of a sensing deviceaccording to an embodiment of the present invention.

FIG. 7 is a timing chart for explaining a driving method of a sensingdevice according to an embodiment of the present invention.

FIG. 8 is a schematic plan view showing a configuration of a sensingelectrode and a sensing circuit for explaining a table TA (TABLE A (TA))drive among the driving methods of a sensing device according to anembodiment of the present invention.

FIG. 9 is a schematic plan view showing a configuration of a sensingelectrode and a sensing circuit for explaining a table TB (TABLE B (TB))drive among the driving methods of a sensing device according to anembodiment of the present invention.

FIG. 10 is a schematic plan view showing a configuration of a sensingelectrode and a sensing circuit for explaining a table TC (TABLE C (TC))drive among the driving methods of a sensing device according to anembodiment of the present invention.

FIG. 11 is a schematic plan view showing a configuration of a sensingelectrode and a sensing circuit for explaining a table TD (TABLE D (TD))drive among the driving methods of a sensing device according to anembodiment of the present invention.

FIG. 12 is a flowchart for explaining a driving method of a sensingdevice according to an embodiment of the present invention.

FIG. 13 is a timing chart for explaining a noise scan among the drivingmethods of a sensing device according to an embodiment of the presentinvention.

FIG. 14 is a schematic plan view showing a configuration of a sensingelectrode and a sensing circuit for explaining a table TE (TABLE E (TE))drive, a table TF (TABLE F (TF)) drive, a table TG (TABLE G (TG)) drive,and a table TH (TABLE H (TH)) drive, among the driving methods of asensing device according to an embodiment of the present invention.

FIG. 15 is a timing chart for explaining a table TE (TABLE E (TE)) driveamong the driving methods of a sensing device according to an embodimentof the present invention.

FIG. 16 is a timing chart for explaining a table TF (TABLE F (TF)) driveamong the driving methods of a sensing device according to an embodimentof the present invention.

FIG. 17 is a timing chart for explaining a table TG (TABLE G (TG)) driveamong the driving methods of a sensing device according to an embodimentof the present invention.

FIG. 18 is a timing chart for explaining a table TH (TABLE H (TH)) driveamong the driving methods of a sensing device according to an embodimentof the present invention.

FIG. 19 is a diagram for explaining an example of step 409 (S409) of adriving method of a sensing device according to an embodiment of thepresent invention.

FIG. 20 is a diagram for explaining an example of step 411 (S411) of adriving method of a sensing device according to an embodiment of thepresent invention.

FIG. 21 is a diagram for explaining an example of step 411 (S411) of adriving method of a sensing device according to an embodiment of thepresent invention.

FIG. 22 is a diagram for explaining an example of step 413 (S413) of adriving method of a sensing device according to an embodiment of thepresent invention.

FIG. 23 is a diagram for explaining an example of step 415 (S415) of adriving method of a sensing device according to an embodiment of thepresent invention.

FIG. 24 is a flowchart for explaining a driving method of a sensingdevice according to a second embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings and the like. However, the present inventioncan be implemented in many different aspects, and should not beconstrued as being limited to the description of the embodimentsexemplified below. In order to make the description clearer, althoughthe drawings may be schematically represented with respect toconfigurations and the like of the respective parts as compared withactual embodiments, they are merely examples, and do not limit theinterpretation of the present invention. Further, in the presentspecification and the drawings, the same symbols (or symbols denoted byA, B, a, b, and the like after numbers) are given to elements similar tothose described above with respect to the above-mentioned figures, anddetailed description thereof may be omitted as appropriate. The terms“first” and “second” appended to each element are convenience signs usedto distinguish each element, and do not have any further meaning unlessotherwise specified.

Not only a contact-type sensing device for specifying the position of asensing object by the sensing object contacting a detection surface ofthe sensing device, but also a so-called hover detection (proximitydetection/non-contact-type detection) sensing device for sensing theproximity state of the sensing object even in a state where the sensingobject does not touch the detection surface is known as a sensing devicefor sensing the position of a sensing object. For example, a sensingdevice having a hover detection function includes a plurality ofdetection electrodes spread over the detection surface. Capacitance isformed between the sensing object and each detection electrode, which isseparated from the detection surface. In this type of sensing device,although it is necessary to sense a subtle change in capacitance inorder to three-dimensionally specify the position of the sensing object,there is a possibility that the accuracy of specifying the sensedposition may decrease due to unexpected noise input from the sensingobject itself or the surroundings.

An embodiment of the present disclosure is to provide a noise-reducedsensing device and a driving method of the sensing device.

A noise-reduced sensing device and a driving method of the sensingdevice will be exemplified in some embodiments described below.

1. First Embodiment 1-1. Configuration of Sensing Device 10

FIG. 1 is a schematic plan view showing an embodiment of a sensingdevice 10.

As shown in FIG. 1 , the sensing device 10 includes a sensing panel 100and a flexible printed circuit board 200. The sensing panel 100 includesa substrate 20, a proximity sensor unit 120 on the substrate 20, and aperipheral area 150 surrounding the proximity sensor unit 120.

A plurality of proximity sensors HS having a sensing electrode 130 isarranged in the proximity sensor unit 120. The plurality of proximitysensors HS is arranged in a matrix in a left-right direction (rowdirection, direction X) and a vertical direction (column direction,direction Y). Each of the plurality of sensing electrodes 130 iselectrically connected to a terminal 140 using a wiring 110. Each of theplurality of sensing electrodes 130 is electrically connected to asensing circuit 300 using a wiring 112 included in the terminal 140 andthe flexible printed circuit board 200.

In addition, each sensing electrode 130 may be connected to a pluralityof wirings 110 from the viewpoint of redundancy. However, when onesensing electrode 130 is connected to the plurality of wirings 110, theplurality of wirings is constantly supplied with the same signal.

The flexible printed circuit board 200 is electrically connected to thesensing panel 100 via a plurality of terminals 140. The sensing circuit300 and an arithmetic circuit 400 are arranged on the flexible printedcircuit board 200. For example, the sensing circuit 300 and thearithmetic circuit 400 are electrically connected to the flexibleprinted circuit board 200 by a COF (Chip on Film) method.

In addition, the sensing circuit 300 and the arithmetic circuit 400 maybe arranged on another circuit substrate connected to the flexibleprinted circuit board 200.

M×n sensing electrodes 130 are arranged in m columns and n rows in theembodiment shown in FIG. 1 . The coefficient m and the coefficient n arepositive integers. In addition, each of the plurality of sensingelectrodes 130 is represented by the sensing electrode (m, n), where (m,n) are the coordinates of each of the plurality of sensing electrodes130. For convenience, it is assumed that the sensing electrode 130 atthe upper left of FIG. 1 is (1, 1) and the sensing electrode 130 at thelower right is (m, n) (in the present embodiment, m=8, n=4).

The sensing circuit 300 includes a sensing signal amplifier circuit 310and an AD converter circuit 320. The sensing signal amplifier circuit310 has at least the same number of amplifier circuit units 316 as thesensing electrode 130, and each amplifier circuit unit 316 is connectedto the wiring 110 one-to-one. The AD converter circuit 320 includes thesame number of AD converters 322 and signal processing circuits 330 asthe sensing electrode 130. Each AD converter 322 is connected to anoutput of the amplifier circuit unit 316 one-to-one, and the signalprocessing circuit 330 and an output of the AD converter 322 areconnected one-to-one. In addition, an output of the signal processingcircuit is connected to the arithmetic circuit 400 via one or aplurality of wirings.

For example, the circuit unit including the amplifier circuit unit 316and the AD converter 322 may be referred to as an Analog Front End(AFE). The sensing circuit 300 has the same number of AFEs as thesensing electrode 130, and they are connected one-to-one via the wiring110.

<1-2. Embodiment of Detection of Voltage Change in Self-CapacitanceMethod>

FIG. 2 is a circuit diagram conceptually showing the sensing electrode130 and a circuit configuration around the AFE connected to the sensingelectrode 130.

As shown in FIG. 2 , the sensing electrode 130 is connected to an inputunit of the AFE via the wiring 110. In addition, the sensing electrode130 has an inherent capacitance (parasitic capacitance C1) in relationto surrounding electrodes or the like. The AFE has a first analogamplifier 314, and an inverting terminal of the first analog amplifier314 is connected to the sensing electrode via a switch 312 and thewiring 110. In addition, a drive signal VCM or a predetermined fixedpotential (Low potential) is input to a non-inverting input terminal ofthe first analog amplifier 314. The fixed potential may be apredetermined constant potential or a ground potential (GND). Inaddition, a back follower capacitor C3 and a reset switch 313 arearranged in parallel between the output terminal side and the invertinginput terminal side of the first analog amplifier 314, and a negativefeedback circuit is formed. In addition, an output of the first analogamplifier 314 is connected to an input of a second analog amplifier 315.An output of the second analog amplifier 315 is electrically connectedbetween the AD converters 322 included in the AD converter circuit 320.For example, the first analog amplifier 314 is a comparator circuit andthe second analog amplifier 315 is an amplifier circuit, in the presentembodiment. However, the configuration and the function of the firstanalog amplifier 314 and the second analog amplifier 315 are not limitedto the configuration and the function shown here as long as they havethe configuration and the function of amplifying an input signal.

FIG. 3 is a schematic cross-sectional view of the sensing panel 100,which is a cross-sectional view of an area indicated by A1 and A2 shownin FIG. 1 . As shown in FIG. 3 , the sensing panel 100 includes thesubstrate 20, a sensing electrode layer 30, a protective film 32, acover layer 40, and a shield electrode 50.

The sensing electrode layer 30 includes the plurality of wirings 110 andthe sensing electrode 130 electrically connected to the wirings 110. Thewiring 110 and the sensing electrode 130 are arranged on the substrate20 in the same layer.

Although the sensing electrode layer 30 may be formed of a single layerof a transparent conductive film such as an ITO, it may also be formedby stacking a metal layer made of mesh or the like on the transparentconductive film. In addition, the sensing electrode layer 30 can beformed only of a metal layer made of mesh or the like. Further, the term“metal layer” as used herein includes not only a configuration composedof a single layer of a single metal or an alloy composed of a pluralityof metals but also a configuration obtained by stacking a plurality ofsuch metal films.

The protective film 32 is arranged over the entire surface of thesubstrate except for the upper surface of the terminal 140, and coversthe wiring 110 and the sensing electrode 130. Further, the protectivefilm 32 includes one layer or a plurality of layers of an inorganic filmand may include a structure in which one layer or a plurality of layersof an organic film and one layer or a plurality of layers of theseorganic films and inorganic films are stacked.

The cover layer 40 is arranged on the protective film 32. The coverlayer protects the sensing electrode layer 30. For example, the coverlayer 40 is a cover glass or a film or thin plate made of a transparentresin. For example, the cover layer 40 and the sensing electrode layer30 are bonded by a transparent adhesive layer (not shown) arrangedtherebetween.

The shield electrode 50 is arranged on a surface of the substrate 20opposite to the surface on which the sensing electrode layer 30 isarranged and is arranged over at least the proximity sensor unit 120 andthe peripheral area 150 including the proximity sensor unit 120. Theshield electrode 50 is electrically connected to the sensing circuit 300and receives a shield signal having a predetermined voltage from thesensing circuit 300. The shield electrode 50 shields an unintendedsignal, an electric field, or the like from the outside of the sensingdevice 10.

Although details will be described later, the sensing device 10 may be acontact-type sensing device for specifying the position of a sensingobject 390 when the sensing object 390 contacts a detection surface 102of the sensing device 10, and may be a so-called hover detection(proximity detection/non-contact-type detection) sensing device forsensing the proximity state of the sensing object 390 even in a statewhere the sensing object 390 does not touch the detection surface 102.

1-3. Functional Configuration of Sensing Device 10

A functional configuration of the sensing device 10 will be describedwith reference to FIG. 2 and FIG. 4 . FIG. 4 is a block diagram showinga functional configuration of the sensing device 10. The configurationof the sensing device 10 shown in FIG. 4 is an example, and theconfiguration of the sensing device 10 is not limited to theconfiguration shown in FIG. 4 . Descriptions of the same or similarconfigurations as those in FIG. 1 to FIG. 3 will be omitted.

The sensing device 10 is a self-capacitance type capacitive sensingdevice. More specifically, the sensing device 10 supplies the drivesignal VCM to the plurality of sensing electrodes 130 to generate acapacitance C2 between the sensing object 390 (for example, a user'sfinger) and the sensing electrode and detects a change in thecapacitance C2 to sense the position of the sensing object 390. Inaddition, the sensing device 10 of the present embodiment performs ahover detection operation (proximity detection/non-contact-typedetection) for sensing the position of the sensing object 390 in a statewhere the sensing object 390 is separated from the sensing electrode 130(the cover layer 40). In this case, location information of the sensingobject 390 is not only two-dimensional information (planar locationinformation) on the proximity sensor unit 120, but alsothree-dimensional information (planar location information and heightinformation) including a distance from the proximity sensor unit 120.The location information of the sensing object 390 in a state in whichthe sensing object 390 is near the proximity sensor unit 120 (the coverlayer 40) so as to be in contact or nearly in contact is only planarlocation information without height information.

The sensing device 10 of the present embodiment that performs the hoverdetection operation has three drive modes (MODE). The three drive modesare a baseline scan, a noise scan, and a signal scan.

The baseline scan is a scan for sequentially or simultaneously inputtingan initial drive signal to the plurality of sensing electrodes 130 andoutputting an initial signal Vini from the amplifier circuit unit 316.

The noise scan is a scan for outputting a sensing signal Vdet1 from theamplifier circuit unit 316 when a predetermined fixed potential is inputto the plurality of sensing electrodes 130.

The signal scanning is a scan for outputting a sensing signal Vdet2 fromthe amplifier circuit unit 316 when sequentially or simultaneouslyinputting a predetermined drive signal to the plurality of sensingelectrodes 130.

For example, the initial signal Vini, a plurality of sensing signalsVdet1, and a plurality of sensing signals Vdet2 are analog signals(analog data). Since the initial drive signal of the baseline scan isequal to a drive signal of the signal scan, these signals will bedescribed simply as the drive signal VCM, in the following description.Although the drive signal VCM is described as an AC square wave with apredetermined period and amplitude, an AC wave that is not a square wave(pulsed wave) may also be adopted, in the following description.

Each of a plurality of initial output signals Vouta, a plurality ofoutput signals Voutb, and a plurality of output signals Voutc isreferred to as low data (RawData), in the present embodiment.

The noise entering the sensing electrode 130 through the sensing objectmay be referred to as, for example, charger noise. The charger noise hasvarious frequencies, and may have a frequency of the drive signal VCMsupplied to each sensing electrode 130 and a sampling frequency that issupplied to a read-out circuit (AFE) for sampling the sensing signal, ora frequency that is approximated to an integral multiple of thesefrequencies.

In this case, the capacitance formed between the sensing electrode 130and the sensing object 390 may change due to the mixing of the chargernoise, making it impossible to obtain the desired sensing signal. Inaddition, if the above-described charger noise is mixed into thecapacitance detection according to the sensing electrode 130 and thesensing object 390, it is difficult to determine the noise or todistinguish between the noise and the desired sensing signal.

The sensing device 10 prepares a plurality of sets of combinations ofdrive signals and sampling signals having the same frequency atdifferent frequencies, executes the noise scan by driving differentproximity sensors HS at the plurality of sets of frequencies, and thenexecutes a signal scan by driving all the proximity sensors HS at onefrequency in the plurality of sets, in the present embodiment. Thesensing device 10 calculates the noise amount sensed by each of theplurality of sensing electrodes 130 using the data obtained by executingthe baseline scan, the data obtained by executing the noise scan, andthe data obtained by executing the signal scan. The sensing device 10detects the presence or absence of noise (charger noise) in relation tothe frequency in the signal scan based on the sensed noise amount, andchanges the frequency of the signal scan as necessary (frequencyhopping).

Hereinafter, the configuration of the sensing circuit for executing thedetection method and the driving of the sensing device will be describedin detail.

1-3-1. Functional Configuration of Sensing Circuit 300

The functional configuration of the sensing circuit 300 will bedescribed with reference to FIG. 2 and FIG. 4 to FIG. 6 . FIG. 5 is atiming chart for explaining a driving method of the sensing device 10.Descriptions of the same or similar configurations as those in FIG. 1 toFIG. 4 will be omitted.

As shown in FIG. 4 , the sensing circuit 300 includes the sensing signalamplifier circuit 310, the AD converter circuit 320, and a sense timingcontrol circuit 340. The sensing signal amplifier circuit 310 and the ADconverter circuit may be collectively referred to as the read-outcircuit (AFE), and the sense timing control circuit 340 may be referredto as the control circuit.

The sensing signal amplifier circuit 310 includes at least the samenumber of amplifier circuit units 316 as the number of proximity sensorsHS, and each amplifier circuit unit 316 outputs a plurality of initialsignal Vini, the plurality of sensing signals Vdet1, and the pluralityof sensing signals Vdet2 based on the drive signal VCM to be input andthe capacitance formed by the connected sensing electrode 130.

The AD converter circuit 320 includes at least the same number of ADconverters 322 and signal processing circuits 330 as the number ofproximity sensors HS. Each AD converter 322 has a function of samplingeach of a plurality of analog signals serially supplied from eachamplifier circuit 316 of the sensing signal amplifier circuit 310according to an intervention of a sampling control signal SAMP, andconverting each of a plurality of sampled analog signals into a digitalsignal. The AD converter 322 serially supplies the digital signal to thesignal processing circuit 330.

For example, the signal processing circuit 330 includes a memory devicesuch as a digital signal processor (DSP), volatile memory, andnon-volatile memory. For example, the digital signal processor includesa multiplier and an adder. The signal processing circuit 330 accumulatesand arithmetically processes digital signals sequentially output fromthe AD converter circuit 320, and outputs them as the initial outputsignal Vouta, the output signal Voutb, and the output signal Voutc tothe arithmetic circuit 400 according to the type of scanning.

For example, the arithmetic processing in the signal processing circuitincludes a process of calculating the difference of the even-numbereddigital signal from the odd-numbered digital signal adjacent to eachother using the digital signal serially output from each AD convertercircuit 320 and calculating the average value of the digital signal inthe period by dividing the difference by the total number of digitalsignals, and outputting the average value as the output signal Vout.

The output signal is output from the sensing circuit 300 to thearithmetic circuit 400 after the end of each scan period. Morespecifically, the sensing device 10 of the present embodiment has abaseline scan period, a noise scan period, and a signal scan period, andthese are executed in a time-division manner. For example, as shown inFIG. 5 , the baseline scan period is arranged first, and after that, thenoise scan period and the signal scan period are alternately arranged aplurality of times, in the sensing device 10 of the present embodiment.Each scan in each scan period is executed a plurality of times for eachproximity sensor HS according to a drive frequency (sampling frequency),and the plurality of digital signals is integrated into the signalprocessing circuit 330. The signal processing circuit 330 generates theoutput signal Vout based on the integrated digital signal, and outputsthe output signal Vout to the arithmetic circuit 400 after the end ofthe scan period.

Further, the noise scan period and the subsequent signal scan period arecollectively referred to as a one frame (1 Frame) period. Although theoutput signals Voutb and Voutc are output to the arithmetic circuit 400for each scan period, integrating the output signals Voutb and Voutcover a plurality of frames in the arithmetic circuit 400 is referred toas frame integration of the output signal.

In addition, the output signals Vouta, Voutb, and Voutc are held in adata holding circuit 450 included in the arithmetic circuit 400.

As shown in FIG. 2 or FIG. 4 , the sense timing control circuit 340supplies the control signal to the sensing signal amplifier circuit 310and the AD converter circuit 320 to control them. More specifically, thesense timing control circuit supplies a connection switch control signalSSW, a reset switch control signal RSW, and the drive signal VCM to eachamplifier circuit unit 316 of the sensing signal amplifier circuit 310.In addition, the sense timing control circuit supplies the samplingcontrol signal SAMP to each AD converter 322 of the AD converter circuit320. The reset switch control signal RSW and the sampling control signalSAMP are synchronized. In addition, the drive signal VCM and the resetswitch control signal RSW are also correlated.

Further, the sense timing control circuit 340 has a function of changingthe frequency of the reset switch control signal RSW, the samplingcontrol signal SAMP, and the scan control signal (the drive signal VCM).To perform such a function, the sense timing control circuit 340 storesa driving table T for the frequencies of the drive signal VCM and thesampling control signal SAMP in the memory. The sense timing controlcircuit 340 has a function of supplying a control signal Hint to thearithmetic circuit 400 and controlling the arithmetic circuit 400.

FIG. 6 shows an example of the driving table T. The driving table T is alook up table (LUT) in which a plurality of drive conditions (tables)for executing each scan of the sensing device 10 is stored. The drivingtable T has a plurality of tables, and each table has a frequency (drivefrequency) of the drive signal VCM supplied to the amplifier circuitunit 316, the reset switch control signal RSW for operating the resetswitch 313 of the amplifier circuit unit 316, and a frequency (samplingfrequency) of the sampling control signal SAMP for instructing samplingin the AD converter 322. For example, the sense timing control circuit340 reads out a program from the memory, and reads out the drivecondition (each frequency) from the driving table T based on the readout program. The sense timing control circuit 340 executes each scanusing the drive condition.

As shown in FIG. 6 , the sensing device 10 includes four driveconditions of the noise scan and four drive conditions of the signalscan as an example. Also, the same drive condition as the signal scan isused for the baseline scan.

The noise scan includes four driving tables: a table TA (table A), atable TB (table B), a table TC (table C), and a table TD (table D).

The signal scan includes four driving tables: a table TE (table E), atable TF (table F), a table TG (table G), and a table TH (table H).

The tables TA to TD of the noise scan are supplied with a predeterminedfixed potential such as GND to the amplifier circuit unit 316, so thereis no specific drive frequency (in FIG. 6 , the drive frequency is shownas Low fixed). In addition, each sampling frequency of the tables TA toTD is FA, FB, FC, and FD, and these are different frequencies. Thesampling frequency FA in the present embodiment is the smallest andincreases in the order of the FB, FC, and FD.

In addition, the drive frequency and the sampling frequency in the tableTE of the signal scan are as same as the sampling frequency FA, which isthe same as the sampling frequency of the table TA of the noise scan.Similarly, the drive frequency and the sampling frequency of each tableTF to TH are as same as the sampling frequency FB, FC and FDrespectively, and these correspond to the sampling frequency FB, FC, andFD in each table TB, TC, and TD of the noise scan. For example, thesefrequencies are several kHz or more and several hundred kHz or less.

1-3-2. Functional Configuration of Arithmetic Circuit 400

The functional configuration of the arithmetic circuit 400 will bedescribed with reference to FIG. 4 . The arithmetic circuit 400 includesthe data holding circuit 450, a PP (peak-to-peak) value calculationcircuit 410, a frame average value calculation circuit 420, a noiseamount calculation circuit 430, and a noise amount comparisondetermination circuit 440.

The number of integrated frames is the number obtained by integratingthe number of signal scans repeatedly executed within one frame in aplurality of frames, in the present embodiment.

For example, the PP value calculation circuit 410 receives the outputsignal Voutb from the data holding circuit 450. For example, the PPvalue calculation circuit 410 integrates the output signal Voutb for apredetermined number of frames for each proximity sensor HS, performs aPeak-Peak calculation by using the integrated output signal Voutb, thatis, calculates a difference between the maximum value and the minimumvalue of the output signal Voutb integrated for each proximity sensorHS, and stores the calculated value as a PP value for each proximitysensor HS. In addition, the PP value calculation circuit 410 transmitsthe PP value to the noise amount calculation circuit 430 and the noiseamount comparison determination circuit 440.

For example, the frame average value calculation circuit 420 stores theoutput signal Vouta for each proximity sensor HS. In addition, forexample, the frame average value calculation circuit 420 receives theoutput signal Voutc from the data holding circuit 450, integrates theoutput signal Voutc for a predetermined number of frames (for example,10 frames) for each proximity sensor HS (frame integration), calculatesan average value of the output signal Voutc by dividing the integrateddata by the number of frames, calculates a difference between theaverage value and the output signal Vouta, and stores the calculatedvalue as an average value AVE for each proximity sensor. In addition,the frame average value calculation circuit 420 transmits the averagevalue AVE to the noise amount calculation circuit 430 and the noiseamount comparison determination circuit 440.

Further, the calculation in the frame average value calculation circuit420 may be configured to calculate the average value AVE by calculatingthe difference in the output signal Vouta with respect to the outputsignal Voutc, integrating and averaging the calculated value.

The noise amount calculation circuit 430 receives the PP values and theaverage values AVE of each proximity sensor from the PP valuecalculation circuit 410 and the frame average value calculation circuit420. The noise amount calculation circuit 430 performs a calculation ofdividing the PP value by the average value AVE for each proximitysensor, and calculates (generates) a noise amount N (FIG. 22 ) from thecalculation. The noise amount calculation circuit 430 transmits thegenerated noise amount N to the noise amount comparison determinationcircuit 440.

The noise amount comparison determination circuit 440 determines a noiseamount for each proximity sensor HS by using the generated noise amountN, and specifies a proximity sensor HS having a sensing signal which isconsidered to contain noise. The noise amount comparison determinationcircuit 440 transmits the presence or absence of the proximity sensor HSdetermined to be noise mixed and the position of the proximity sensor HSto the sensing circuit 300 as a determination result Vjr.

The sensing circuit 300 determines whether the drive frequency and thesampling frequency of the signal scan can be changed based on thedetermination result Vjr, and when it is determined that they can bechanged, changes the drive frequency and the sampling frequency of thesignal scan based on the driving table T (frequency hopping).

As described above, the sensing device 10 of the present embodiment hasthe three drive modes (MODE). The three drive modes are the baselinescan, the noise scan, and the signal scan described above. Each drive inone proximity sensor HS will be described in detail below. Further, itis assumed that the baseline scan and the signal scan are executed basedon the table TE, and the noise scan is executed based on the table TA,in the following explanation.

The drive signal VCM of an FA drive frequency is supplied to the firstanalog amplifier 314, and the reset switch control signal RSW having thesame drive frequency FA is supplied to the reset switch 313, in thebaseline scan. That is, the amplifier circuit unit 316 is driven by thedrive frequency FA. In addition, the sampling control signal SAMP of thesampling frequency FA is supplied to the AD converter 322, and the ADconverter 322 executes the sampling of the analog signal Vini outputfrom the amplifier circuit unit 316 based on the sampling frequency FA.That is, the drive signal VCM, the reset switch control signal RSW, andthe sampling control signal SAMP are synchronously driven at the drivefrequency FA, and the digital signal output from the AD converter 322 isserially accumulated in the signal processing circuit 330 until thebaseline scan period ends.

The base line scan driving is performed in a state in which there is nosensing object 390. A high (High, H) voltage is supplied to the resetswitch control signal RSW when the drive signal VCM is at a low (Low, L)voltage, whereby the switch 113 is turned on, the input terminal and theoutput terminal of the first analog amplifier 314 become conductive, andthe amplifier circuit unit is reset. In this case, the charges chargedin a capacitance C3 are discharged. In addition, a low voltage issupplied to the reset switch control signal RSW when the drive signalVCM is at a high voltage, whereby the switch is turned off, the inputterminal and the output terminal of the first analog amplifier 314become non-conductive, charges corresponding to the capacitance C1 ofthe sensing electrode 130 are charged in the back follower capacitor C3,and a potential corresponding to the capacitance of the back followercapacitor C3 is output from the first analog amplifier 314. The outputsignal is amplified by the second analog amplifier 315 to become theanalog signal Vini, and supplied to the AD converter circuit 320. Inthis case, a high-voltage sampling control signal SAMP is supplied, andthe analog signal Vini is sampled by the AD converter circuit 320 andconverted into a digital signal. The digital signal is accumulated inunits of frames in the signal processing circuit and subjected toarithmetic processing, and then output to the arithmetic circuit 400 asVouta.

Further, at the time of the base line scan driving, a drive signal VCMthe same as the drive signal VCM supplied to the proximity sensor HS issupplied to the shield electrode 50.

The plurality of proximity sensors HS is driven based on the table TA inthe noise scan. Although the drive basically performs the same drive asthe baseline scan, the sampling control signal SAMP has a predetermineddrive frequency FA, while the drive signal VCM and the reset switchcontrol signal RSW are predetermined fixed potentials (Low fixed). Inaddition, driving the amplifier circuit unit 316 and the AD converter322 based on such a signal makes the amplifier circuit unit 316 outputan analog signal Vdet1, and the analog signal Vdet1 is sampled at thedrive frequency FA and converted into a digital signal in an ADconverter 422. The digital signal is accumulated in units of frames inthe signal processing circuit 330 and subjected to arithmeticprocessing, and then output to the arithmetic circuit 400 as Voutb.

Further, at the time of the noise scan driving, a predetermined fixedpotential is supplied to the shield electrode 50 as in the case of theproximity sensor HS.

The same driving as in the baseline scan is performed in the signalscan. That is, the reset switch control signal RSW and the samplingcontrol signal SAMP have the drive frequency FA, and the scan controlsignal (the drive signal VCM) also has the drive frequency FA. Inaddition, the output from the amplifier circuit unit 316 is an analogsignal Vdet2, and the analog signal Vdet2 is sampled at the drivefrequency FA and converted into a digital signal in the AD converter322, in the signal scan. The digital signal is accumulated in units offrames in the signal processing circuit 330 and subjected to arithmeticprocessing, and then output to the arithmetic circuit 400 as Voutc.

Further, at the time of the signal scan line driving, the same drivesignal VCM as the drive signal VCM supplied to the proximity sensor HSis supplied to the shield electrode 50.

Although the baseline scan is performed in a state in which the sensingobject 390 is not positioned on the detection surface 102 (for example,immediately after the sensing device 10 is activated), and the like, thenoise scan and the signal scan are performed in a time-division mannerregardless of the presence or absence of the sensing object 390. In thecase where the sensing object 390 is present during the scanning, thecapacitance C2 is formed between the sensing electrode 130 and thesensing object 390, thereby changing each of the sensing signals Vdet1and Vdet2.

1-4. Driving Method of Sensing Device 10

A method of driving the sensing device 10 will be described withreference to FIG. 5 to FIG. 23 . FIG. 7 is a timing chart for explaininga driving method of the sensing device 10. Each of FIG. 8 to FIG. 11 isa schematic plan view showing the configuration of the sensing electrode130 and the sensing circuit 300 for explaining the driving of the tableTA, the driving of the table TB, the driving of the table TC, thedriving of the table TD, and the driving of the tables TE to TH, in thedriving method of the sensing device 10. FIG. 12 is a flowchart forexplaining the driving method of the sensing device 10. FIG. 13 to FIG.18 are timing charts for explaining the driving of the tables TA to TD,the driving of the table TE, the driving of the table TF, the driving ofthe table TG, and the driving of the table TH, in the driving method ofthe sensing device 10.

FIG. 19 to FIG. 23 are diagrams for explaining an example of each stepof the driving method of the sensing device 10. The configuration andthe driving method of the sensing device 10 shown in FIG. 5 to FIG. 23are examples, and the configuration and the driving method of thesensing device 10 are not limited to the configurations shown in FIG. 5to FIG. 23 . Descriptions of the same or similar configurations as thosein FIG. 1 to FIG. 4 will be omitted.

In the timing chart shown in FIG. 5 , the states of the drive modes(MODE), a control signal HD, the control signal Hint, and the arithmeticcircuit 400 of the sensing device 10 are shown with respect to time(Time) on the horizontal axis.

The sensing device 10 executes the three drive modes of the baselinescan, the noise scan, and the signal scan in a time-division manner. Thebaseline scan is executed in an initial setting period OP1, the noisescan is executed in a first sensing period OP2, and the signal scan isexecuted in a second sensing period OP3. Also, the baseline scan periodcorresponds to the initial setting period OP1, the noise scan periodcorresponds to the first sensing period OP2, and the signal scan periodcorresponds to the second sensing period OP3.

The control signal HD is, for example, a signal that serves as areference (trigger) for executing each scan. The control signal Hint isa signal that serves as a reference (trigger) for reading out theinitial output signal Vouta (for example, first sensed data RD1), theoutput signal Voutb (for example, second sensed data RD2), and theoutput signal Voutc (for example, third sensed data RD3) for eachsensing electrode 130 stored in the signal processing circuit 330.

When the sensing device 10 starts a proximity sensing operation, first,the baseline scan is executed in the initial setting period OP1. Afterthe baseline scan is executed, the noise scan and the signal scan arealternately executed. The noise scan and the signal scan are repeatedlyexecuted.

The first sensing period OP2 and the second sensing period OP3 arereferred to as frame (Frame) periods, e.g., repeated frame periods arereferred to as a first frame (1st Frame) period, a second frame (2ndFrame) period, . . . , and a kth frame (k-th Frame) period, in anembodiment of the present invention. The coefficient k is a positiveinteger. For example, the sensing device 10 executes the proximitysensing operation for k times of frame periods. The frame (Frame) periodis executed, for example, at a frequency of 60 Hz or higher and afrequency of 180 Hz or lower, and one frame period is, for example, 5.5ms or more and 16.6 ms or less. The frame (Frame) period is executed ata frequency of 120 Hz and one frame period is 8.3 ms, in an embodimentof the present invention.

The sensing device 10 executes the baseline scan at a sampling frequencybased on the driving table in synchronization with the control signalHD, in the initial setting period OP1. The sensing device 10 mayexecute, for example, a first scan (1st scan), a second scan (2nd scan),. . . , and a pth scan (p-th scan), i.e., scans p number of times,within the initial setting period OP1 in the baseline scan. Thecoefficient p is a positive integer.

The sensing device 10 executes the noise scan following the baselinescan at a sampling frequency based on the driving table T insynchronization with the control signal HD, in the first sensing periodOP2. The sensing device executes, for example, the first scan (1stscan), the second scan (2nd scan), . . . , and a qth scan (q-th scan),i.e., scans q number of times. The coefficient q is a positive integer,in the noise scan. As will be described later, the number of noise scansin the first sensing period OP2 varies depending on the proximity sensorHS.

The sensing device 10 executes the signal scan following the noise scanat a sampling frequency based on the driving table T in synchronizationwith the control signal HD, in the second sensing period OP3. Thesensing device 10 executes, for example, the first scan (1st scan), thesecond scan (2nd scan), . . . , and an rth scan (r-th scan), i.e., scansr number of times, within the second sensing period OP3, in the signalscan. The coefficient r is a positive integer.

For example, when the control signal Hint is supplied from the sensingcircuit 300, the arithmetic circuit 400 transitions to a read-out state(READ state). The arithmetic circuit 400 reads out the output signalVout (for example, first sensed data RD0) of each sensing electrode 130temporarily stored in the memory device included in the signal processorcircuit 330 in synchronization with the control signal Hint.

FIG. 7 is a diagram showing an embodiment of a driving table executed inthe noise scan and the signal scan in the timing chart shown in FIG. 5 .

As shown in FIG. 7 , for example, driving (first driving to fourthdriving) using the table TA to the table TD is executed in parallel inthe noise scan period executed in the first sensing period OP2. Morespecifically, as shown in FIG. 8 , the proximity sensor HS correspondingto (2 i-1, 2 j-1) among the proximity sensors executes the noise scanbased on the table TA. In addition, as shown in FIG. 9 , the proximitysensor HS corresponding to (2 i-1, 2 j) executes the noise scan based onthe table TB during the noise scan. Further, as shown in FIG. 10 , theproximity sensor HS corresponding to (2 i, 2 j-1) executes the noisescan based on the table TC during the noise scan. In addition, as shownin FIG. 11 , the proximity sensor HS corresponding to (2 i, 2 j)executes the noise scan based on the table TD during the noise scan.Since the drive frequency and the sampling frequency are different fromeach other, the number of scans is different for each proximity sensorHS driven in each table.

As shown in FIG. 7 , for example, the signal scan based on one table(for example, the table TE) of the table TE to TH is executed for allsensing electrodes in the signal scan period executed in the secondsensing period OP3.

The sensing device 10 according to an embodiment of the presentinvention simultaneously executes the noise scan for four frequenciesusing four drive frequencies and four sampling frequencies based on thenoise scan using the driving of the table TA to TD. In addition, as willbe described later, the sensing device 10 according to an embodiment ofthe present invention executes the signal scan based on one table amongthe tables TE to TH. The presence or absence of noise in relation to thefour drive frequencies is sensed based on the sensing signal obtained ineach scan, and the sensing object 390 is sensed.

Further, the configuration of the driving table according to anembodiment of the present invention is an example, and is not limited tothe example shown here. For example, in the case where noise for eightfrequencies is checked using the driving table based on eight drivefrequencies and eight sampling frequencies, the plurality of sensingelectrodes 130 is divided into eight groups and controlled by the sensetiming control circuit 340 to drive in response to each of the eightdriving tables within one frame period.

For example, in the case where noise for eight frequencies is checkedusing the driving table based on eight drive frequencies and eightsampling frequencies, the plurality of sensing electrodes 130 may bedivided into four and controlled by the sense timing control circuit 340to drive in response to each of the four driving tables among the eightdriving tables in a half period of one frame period and drive inresponse to each of the four driving tables among the remaining eightdriving tables in a half period of one frame period.

The sensing device 10 according to an embodiment of the presentinvention may be configured such that each of the noise scan and thesignal scan includes at least two or more driving tables, and the signalsensed by each proximity sensor HS (the sensing electrode 130) can becontrolled using different drive frequencies and sampling frequencies.

Hereinafter, an embodiment of a driving method of the sensing device 10will be described in detail with reference to FIG. 5 and FIG. 8 to FIG.23 . In addition, the baseline scan and the signal scan are performedbased on the initial table TE in the following explanation.

1-4-1. Step 401 (S401)

As shown in FIG. 12 , when the sensing device 10 starts the proximitysensing operation, the sense timing control circuit 340 in the sensingcircuit 300 transmits the control signal HD to each circuit. the sensingdevice 10 executes the baseline scan in the initial setting period OP1,in step 401 (S401) as shown in FIG. 5 . Since the description of thebaseline scan is mainly the same as that described with reference to theconfigurations shown in FIG. 4 to FIG. 7 , detailed descriptions thereofwill be omitted. In the baseline scan, a scan based on the table TEamong the signal scan is executed on all the proximity sensors HS in anon-existence state without the sensing object 390 such as the initialperiod of the proximity sensing operation. The amplifier circuit unit316 of each proximity sensor HS generates the initial signal Vini andtransmits the generated initial signal Vini to the AD converter 322. TheAD converter 322 outputs the digital signal based on the initial signalVini to the signal processing circuit 330. After the digital signalbased on the initial signal Vini is arithmetically processed in thesignal processing circuit 330, the signal processing circuit 330transmits the generated initial output signal Vouta (initial voltage) tothe arithmetic circuit 400.

Although the above-described baseline scan is executed based on thetable TE over the initial setting period OP1, a configuration in which aplurality of initial setting periods OP1 is continuously arranged, andthe scan based on the tables TF, TG, and TH is sequentially executedafter the execution of the baseline scan may be adopted. As a result,the initial output signal Vouta based on the baseline scan of each tableat the beginning of the detecting operation is stored in the arithmeticcircuit 400. In addition, the initial setting period OP1 during whichthe baseline scan is performed may be arranged at an appropriateinterval (for example, at a rate of once in dozens to thousands offrames) as well as at the time of starting up the sensing device.

1-4-2. Step 403 (S403)

The sensing device 10 executes the noise scan based on a predeterminedtable (the tables TA to TD) for each of the proximity sensors HS in thefirst sensing period OP2, as shown in FIG. 8 to FIG. 11 , in step 403(S403) shown in FIG. 12 . FIG. 13 shows the driving timing of each tablein the noise scan period.

As shown in FIG. 13 , the drive signal VCM is fixed to a low voltage(Low, L) in all tables, and a fixed potential is supplied to the firstanalogue amplifier of the amplifier circuit unit 316, in the noise scan.In addition, the connection switch control signal SSW is supplied with ahigh voltage (High, H) and is fixed at a high voltage, so that theswitch 312 is turned on to maintain the connection between the sensingelectrode 130 and the amplifier circuit unit 316.

At a time ta1, the control signal HD changes from a low voltage to ahigh voltage, and at a time ta2, the control signal HD changes from ahigh voltage to a low voltage. As a result, the noise scan periodstarts.

A reset switch control signal RSW_A is supplied with a high voltage fromthe time ta2 to a time ta3, whereby the reset switch 313 is maintainedin the on state, and the amplifier circuit unit 316 is in the resetstate, in driving using the table TA (FIG. 8 ). In addition, a samplingcontrol signal SAMP_A supplied to the AD converter 322 is a low voltage,whereby the AD converter 322 does not perform sampling. Similar to thedriving using the table TA, the table TC (FIG. 10 ), and the table TD(FIG. 11 ), reset switch control signals RSW_B, RSW_C, and RSW_D aresupplied with a high voltage, and sampling control signals SAMP_B,SAMP_C, and SAMP_D are supplied with a low voltage, in driving using thetable TB (FIG. 9 ).

The reset switch control signals RSW_A to RSW_D change from a highvoltage to a low voltage, the reset switch 313 is turned off, the backfollower capacitor C3 is charged, and the sensing signal Vdet1 based onthe capacitance of the back follower capacitor C3 is output from thesecond analog amplifier 315 to the AD converter 322, at the time ta3. Inaddition, after the reset switch 313 is turned off, the connectionswitch control signal SSW supplied to the AD converter 322 becomes a lowvoltage after being supplied with a high voltage, and based on this,each AD converter 322 executes sampling and outputs the digital signalbased on Vdet1 to the signal processing circuit 330.

After that, the sampling control signal SAMP_D is supplied with a lowvoltage, and the reset switch control signal RSW_D is supplied with ahigh voltage, whereby the amplifier circuit unit 316 is reset.

As shown in FIG. 13 , since each table TA to TD has different samplingfrequencies, the timings at which the analog signals are sampled and thetimings at which the amplifier circuit unit 316 are reset are differentfor each table. The sampling frequency of the table TA is the smallest,and increases in order from the tables TB, TC, and TD, in the presentembodiment. As a result, the number of scans differs for each table andthus for each proximity sensor HS.

In addition, the signal processing circuit 330 generates the outputsignal Voutb by performing averaging processing after integrating thedigital signal to be output from the AD converter circuit 320 for thescan period and outputs the generated Voutb to the arithmetic circuit400.

1-4-3. Step 405 (S405)

The sensing device 10 executes the signal scan on all the proximitysensors HS based on the table TE in the second sensing period OP3, asshown in FIG. 14 , in step 405 (S405) shown in FIG. 12 .

The connection switch control signal SSW is fixed at a high voltage forthe applicable period, as shown in FIG. 15 , in the driving using thetable TE, whereby the sensing electrode 130 and the amplifier circuit316 are maintained in a connected state for applicable period.

The control signal HD changes from the low voltage to the high voltageat the time ta1, and the control signal HD changes from the high voltageto the low voltage at the time ta2, as shown in FIG. 15 , in the drivingusing the table TE. As a result, the signal scan period starts.

In addition, a scan drive signal VCM_E changes from a low voltage to ahigh voltage at the time ta1, and changes from a high voltage to a lowvoltage at a time ta4. As described above, the scan drive signal VCM_Eis an AC square wave having a predetermined amplitude and period, andthe scan drive signal VCM_E having such a period is supplied to thefirst analog amplifier 314 of the amplifier circuit unit, in the signalscan using the table TE.

In addition, a reset switch control signal RSW_E is a high voltage, thereset switch 313 is turned on, and the amplifier circuit unit 316 is inthe reset state at the time tat. Further, the sampling control signalSAMP_A is a low voltage and the AD converter circuit 320 does notexecute sampling.

The scan drive signal VCM is still at a high voltage, while the resetswitch control signal RSW_E changes from a high voltage to a lowvoltage, and the reset switch 313 of the amplifier circuit unit 316 isturned off, whereby the capacitance corresponding to the capacitancestate of the sensing electrode 130 is charged to the back followercapacitor C3, and the output based on the capacitance is output from thefirst analog amplifier 314, at the time ta3. In addition, a samplingcontrol signal SAMP_E is supplied with a low voltage, and the ADconverter circuit 320 does not execute sampling at this time.

The scan drive signal VCM_E changes from a high voltage to a low voltageat the time ta4. After the time ta4, the sampling control signal SAMP_Eis once supplied with a high voltage. As a result, at a time ta5, the ADconverter circuit 320 samples the sensing signal Vdet2 output from thesecond analog amplifier 315 (the AFE) using the AD converter 322,converts the sensing signal Vdet2 into a digital signal and outputs itto the signal processing circuit 330 (sampling of the sensing signalVdet2 in the first cycle). After that, at a time ta6, the reset switchcontrol signal RSW_E is turned to a high voltage once, the reset switch313 is in the on state, and after the amplifier circuit unit 316 haspassed through the reset state, the reset switch 313 is returned to thecharge state (amplified state).

After that, at a time ta7, the scan drive signal VCM_E changes from alow voltage to a high voltage, and the sampling control signal SAMP_Ebecomes high again at a time ta8 in the state where the scan drivesignal VCM_E is a high voltage, and the sampling is executed (samplingof the sensing signal Vdet2 in the second cycle). After that, at a timeta9, the reset switch control signal RSW_E is turned to a high voltageonce again, the reset switch 313 is in the on state, and after theamplifier circuit unit 316 has passed through the reset state, the resetswitch 313 is returned to the charge state (the amplified state). Theabove operation is repeated in the signal scan.

In addition, the signal processing circuit 330 generates the outputsignal Voutc by performing averaging processing after integrating thedigital signal to be output from the AD converter circuit 320 for thescan period and outputs the generated Voutc to the arithmetic circuit400.

FIG. 16 shows a timing chart of the driving using the table TF, FIG. 17shows a timing chart of the driving using the table TG, and FIG. 18shows a timing chart of the driving using the table TH. The cycles ofthe drive signal VCM, the sampling control signal SAMP, and the resetswitch control signal RSW are shown in each table of FIG. 6 , and thesame control is executed except that each of them is different, so thatexplanation thereof will be omitted.

1-4-4. Step 407 (S407)

The sensing device 10 determines whether the noise scan using the tablesTA to TD and the signal scan using the table TE have been executed for adesired number of frames (for example, 10 frames), in the first sensingperiod OP2 and the second sensing period OP3, in step 407 (S407) shownin FIG. 12 . That is, the sensing device 10 determines whether the frameintegration is completed. The determination may be executed by the sensetiming control circuit 340 or may be executed by the signal processingcircuit 330.

In addition, in this case, the arithmetic circuit 400 stores the sensingsignal (output signal Vouta) for 10 frames based on any one of the tableTA to the table TD and the sensing signal (output signal Voutb) based onthe table TE for each proximity sensor HS.

The sense timing control circuit 340 or the signal processing circuit330 repeats steps S403 to S407 until the predetermined number of frameintegrations is completed, and when the predetermined number of frameintegrations is completed, shifts the processing to the following stepS409.

1-4-5. Step 409 (S409)

The sensing device 10 calculates the PP value of each proximity sensorHS using the output signal Voutb, in step 409 (S409) shown in FIG. 12 .The calculation of the PP value is executed using the PP valuecalculation circuit 410 included in the arithmetic circuit 400. As shownin FIG. 19 , the PP value calculation circuit 410 extracts the maximumvalue and the minimum value from the number of sensing signals Voutbcorresponding to the number of scans for each proximity sensor HS, andcalculates the difference between the maximal value and the minimumvalue. The calculation result is transmitted as a PP value NSPP (PPvalue NSPP_Rx00 to Rx31) to the noise amount calculation circuit 430 andthe noise amount comparison determination circuit 440.

1-4-6. Step 411 (S411)

The sensing device 10 calculates a frame average value using the outputsignal Voutc and the initial output signal Vouta in step 411 (S411)shown in FIG. 12 . The calculation of the frame average value isexecuted using the frame average value calculation circuit 420 includedin the arithmetic circuit 400. The frame average value calculationcircuit 420 calculates the average value (SSPP_Rx00 to Rx31) of, forexample, 10 times of the sensing signal (output signal Voutc) for eachproximity sensor HS (FIG. 20 ), and calculates the difference betweenthe average value and the sensing signal Vouta (BSTE_Rx00 to Rx31) ofthe baseline scan based on the previously extracted table TE (FIG. 21 ).Alternatively, the frame average value calculation circuit may calculatethe difference between the sensing signal Voutc and the sensing signalVouta of the baseline scan, and then average the difference values of 10times. The calculation result is transmitted as the frame average valueAVE (frame average values AVE_Rx00 to Rx31) to the noise amountcalculation circuit 430 and the noise amount comparison determinationcircuit 440.

In addition, the sensing signal Vouta of the base line scan used in thearithmetic processing is a baseline scan performed in the same table asthe signal scan. In the above description, the sensing signal Vouta ofthe base scan performed based on the table TE is used.

1-4-7. Step 413 (S413)

The sensing device 10 calculates the noise amount using the PP valueNSPP and the frame average value AVE, in step 413 (S413) shown in FIG.12 . The calculation of the noise amount is executed using the noiseamount calculation circuit 430 included in the arithmetic circuit 400.The noise amount calculation circuit 430 obtains the noise amount N(noise amount N_Rx00 to Rx31) in each proximity sensor by dividing thePP value NSPP by the frame average value AVE in units of each proximitysensor HS (FIG. 22 ). The noise amount calculation circuit 430 transmitsa noise amount Ndata to the noise amount calculation circuit 430.

1-4-8. Step 415 (S415), Step 417 (S417) and Step 419 (S419)

The sensing device 10 determines whether to perform frequency hoppingusing the noise amount N, in step 415 (S415), step 417 (S417) and step419 (S419) shown in FIG. 12 . The determination of the noise amount isexecuted using the noise amount comparison determination circuit 440included in the arithmetic circuit 400.

For example, the noise amount comparison determination circuit 440compares the noise amount N for each proximity sensor HS, extracts amaximum value thereof, and determines whether the maximum value isgreater than a predetermined threshold value. When it is determined thatthe maximum value of the noise amount N is greater than the thresholdvalue (YES in step 415 (S415)), the noise amount comparisondetermination circuit 440 specifies a table when the proximity sensor HSthat has extracted the maximum value performs the noise scan, andtransmits the table to the sense timing control circuit 340 as thedetermination result Vjr. The sense timing control circuit 340 refers tothe determination result Vjr and the driving table T, and determineswhether the table obtained as the determination result has the samesampling frequency as the table on which the current signal scanning isperformed. In this case, if they are determined to be the same, it meansthat the frequency of the charger noise extracted as the noise amount isthe same as or approximate to the frequency of the signal scan or aninteger multiple thereof. In this case, the sense timing control circuit340 changes (frequency hopping) from the current signal scan table (thetable TE) to another table (for example, the table TH) based on thedetermination result Vjr, and executes subsequent signal scans based onthat table.

More specifically, for example, as shown in FIG. 23 , it is assumed thatthe noise amount comparison determination circuit 440 determines thatthe noise amount N_Rx18 is the maximum value and is greater than thethreshold value. The noise amount comparison determination circuit 440determines that the noise amount N_Rx18 is a value calculated by thenoise scan using the driving of the table TA (see FIG. 8 ), andtransmits the determination result Vjr to the sensing circuit 300.

The sense timing control circuit 340 included in the sensing circuit 300refers to the stored table T and determines whether the table (the tableTA) obtained from the determination result input from the arithmeticcircuit 400 and the table (the table TE) of the current signal scanshare the sampling frequency. In this case, since the table TA and thetable TE of the current signal scan have the same sampling frequency,the sense timing control circuit 340 changes from the table TE to thetable TH and executes the subsequent signal scan.

In addition, the selection of the frequency may be appropriatelydetermined according to the environment in which the sensing device 10is used, an application, and the like, in the frequency hopping. Forexample, the frequency hopping may be executed using a plurality offrequencies avoiding an even multiple of the frequency similar to thesensed noise, using a plurality of frequencies avoiding an odd multipleof the frequency similar to the sensed noise, and using a plurality offrequencies avoiding a frequency similar to the sensed noise andincluding a frequency similar to the frequency of the noise with thesmallest amount of sensed noise.

Further, the noise amount comparison determination circuit 440 may adopta method of specifying a corresponding proximity sensor HS based only onthe maximum value of the noise amount without having a threshold valueand a table in the proximity sensor HS.

In addition, when it is determined that the maximum value of the noiseamount N is smaller than the threshold value, the noise amountcomparison determination circuit 440 transmits the result to the sensetiming control circuit as the determination result Vjr. In this case,the sense timing control circuit determines that no significant noiseshave been sensed and continues to perform the signal scan based on thecurrent table.

For example, it is assumed that the noise amount N_Rx22 of Rx22 to benoise-scanned based on the table TC is determined to be the maximumvalue and larger than the threshold value. Also in this case, the noiseamount determination circuit 440 specifies the table when the signalscan is performed, and transmits the table to the sense timing controlcircuit 340 as the determination result Vjr. The sense timing controlcircuit 340 refers to the determination result and the table, anddetermines whether the table obtained as the determination result Vjrhas the same sampling frequency as the table on which the current signalscanning is performed. In the above, it is determined that these aredifferent. This means that the frequency (FC) of the charger noiseextracted as the noise amount significantly differs from the frequency(FA) of the signal scan. In this case, the sense timing control circuit340 does not change the table (the table TE) of the current signal scanbased on the determination, and performs subsequent signal scans basedon that table.

After performing the frequency hopping and after not performing thefrequency hopping, the sensing device 10 returns to step 403 (S403) andrepeatedly executes steps 403 (S403) to 419 (S419).

1-5. First Modification of Driving Method of Sensing Device 10

The PP value calculation circuit 410 is included in the sensing circuit300 as compared with the driving method of the sensing device 10 in afirst modification of the driving method of the sensing device 10. Thecalculation of the PP value described in step 409 (S409) is executedusing the PP value calculation circuit 410 included in the sensingcircuit 300, in the first modification.

The time required for the noise scan can be shortened by simultaneouslyperforming the noise scan with at least two different drivingfrequencies, in the sensing device 10 according to an embodiment of thepresent invention.

In addition, the sensing device 10 can detect the position of thesensing object 390 by performing the frequency hopping using anoise-free frequency based on the calculation and determination of thenoise amount even if the noise and signal are slight. As a result, evenwhen the frequency of the noise changes frequently, the sensing device10 changes the drive frequency of the signal scan according to thefrequency, so that it is possible to suppress the noise contaminationduring the signal scan as much as possible.

2. Second Embodiment

A driving method different from the driving method of the sensing deviceaccording to the first embodiment will be described in the secondembodiment of the present invention. The driving method of the sensingdevice 10 according to the second embodiment differs from the drivingmethod of the sensing device according to the first embodiment in thatstep 403′ (S403′) is executed before step 405 (S405) and step 415 (S415)is executed after step 405 (S405). In the driving method of the sensingdevice 10 according to the second embodiment, step 403′ (S403′) will bemainly described, and the same or similar configurations as those of thefirst embodiment will not be described here.

FIG. 24 is a flowchart for explaining a driving method of the sensingdevice 10 according to the second embodiment of the present invention.

The noise scan is executed based on the table TA to the table TDassigned to each proximity sensor HS in the same manner as in the firstembodiment, and the digital signal output from the AD converter 322 byeach scan is accumulated in the signal processing circuit 330, in step403′ (S403′) shown in FIG. 24 , in the noise scan period. In this case,the signal processing circuit 330 further obtains the maximum value andthe minimum value of the accumulated digital signal, calculates thedifference between the maximal value and the minimum value, and outputsthe calculated result to the arithmetic circuit as Voutb′. Thearithmetic circuit 400 replaces Voutb′ with a noise amount N′, comparesthe noise amount with the threshold value in the noise amountcalculation circuit 430 and the noise amount comparison determinationcircuit 440, and specifies the proximity sensor HS and the table thatoutput the noise amount greater than the threshold value. The subsequentprocessing is the same as that of the first embodiment.

According to such a configuration, the PP value calculation circuit 410and the frame average value calculation circuit 420 are not required inthe arithmetic circuit 400, and the processing by the arithmetic circuit400 can be reduced.

Each of the embodiments described above as an embodiment of the presentinvention can be appropriately combined and implemented as long as nocontradiction is caused.

It is understood that, even if the advantageous effect is different fromthose provided by each of the above-described sensing device and thedriving method of the sensing device, the effect obvious from thedescription in the specification or easily predicted by personsordinarily skilled in the art is apparently derived from the presentinvention.

What is claimed is:
 1. A sensing device comprising; a plurality ofsensing electrodes arranged in a row direction and a column direction; asensing circuit including a plurality of read-out circuits respectivelyconnected to the plurality of sensing electrodes and a control circuitconfigured to control the plurality of read-out circuits; and anarithmetic circuit that processes a sensing signal output from thesensing circuit; wherein the plurality of sensing electrodes and theplurality of read-out circuits are connected one-to-one via wiring, thesensing circuit is configured to store a driving table that storesmultiple sampling frequencies different from each other, the controlcircuit is configured to read out the multiple sampling frequencies fromthe driving table, drive simultaneously the plurality of read-outcircuits by using the multiple sampling frequencies, and output aplurality of output signals obtained by the driving to the arithmeticcircuit, and the arithmetic circuit is configured to process theplurality of output signals from the control circuit, and to calculatean amount of noise.
 2. The sensing device according to claim 1, whereineach of the plurality of read-out circuits is configured to detect afirst sensing signal based on an initial drive signal, a second sensingsignal based on a predetermined fixed voltage and a third sensing signalbased on a detection drive signal, the multiple sampling frequenciesinclude at least a first frequency and a second frequency different fromthe first frequency, the plurality of read-out circuits includes a firstread-out circuit and a second read-out circuit, the first read-outcircuit is configured to output a second sensing signal based on asampling frequency of the first frequency, and output a third sensingsignal based on a sampling frequency of the first frequency, the secondread-out circuit is configured to output a second sensing signal basedon a sampling frequency of the second frequency, and output a thirdsensing signal based on a sampling frequency of the first frequency, andthe arithmetic circuit is configured to calculate the amount of noiseusing the second sensing signal and the third sensing signal output fromthe first read-out circuit and the second sensing signal and the thirdsensing signal output from the second read-out circuit.
 3. The sensingdevice according to claim 2, wherein output of a second signal and athird signal by the first read-out circuit is performed a plurality oftimes, output of the second signal and the third signal by the secondread-out circuit is performed a plurality of times, and the arithmeticcircuit is configured to store the second signals and the third signalsfrom the first circuit and the second circuit.
 4. The sensing deviceaccording to claim 3, wherein the detection drive signal includes thefirst frequency.
 5. The sensing device according to claim 4, wherein theinitial drive signal has the first frequency, the first read-out circuitis configured to output a first sensing signal based on a samplingfrequency of the first frequency, and the second read-out circuit isconfigured to output a first sensing signal based on a samplingfrequency of the first frequency.
 6. The sensing device according toclaim 5, wherein the arithmetic circuit is configured to calculate asignal scan value of the sensing electrode based on the first sensingsignal and the third sensing signal output from the first read-outcircuit, and calculate a signal scan value for the sensing electrodebased on the first sensing signal and the third sensing signal outputfrom the second read-out circuit.
 7. The sensing device according toclaim 6, wherein the arithmetic circuit is configured to calculate asignal scan value of the sensing electrode based on the plurality ofsecond sensing signals from the first read-out circuit, and calculate asignal scan value for the sensing electrode based on the plurality ofsecond sensing signals output from the second read-out circuit.
 8. Thesensing device according to claim 7, wherein the arithmetic circuit isconfigured to calculate the presence/absence of noise in the sensingelectrode based on the signal scan value and the noise scan value.
 9. Adriving method of a sensing device, the sensing device including aplurality of sensing electrodes arranged in a row direction and a columndirection, a sensing circuit including a plurality of read-out circuitsrespectively connected to the plurality of sensing electrodes and acontrol circuit for controlling the plurality of read-out circuits, andan arithmetic circuit that arithmetically is configured to process asensing signal output from the sensing circuit; the plurality of sensingelectrodes and the plurality of read-out circuits are connectedone-to-one via wiring; and the sensing circuit is configured to store adriving table that stores multiple sampling frequencies different fromeach other, the method comprising: reading out the multiple samplingfrequencies different from each other; driving simultaneously theplurality of read-out circuits at the multiple sampling frequenciesdifferent from each other; generating a plurality of output signalsobtained by the driving; performing arithmetic processing on theplurality of output signals read out using the multiple samplingfrequencies different from each other; and calculating an amount ofnoise.